1. Field of the Invention
The present invention broadly relates to combustion stability in the afterburner system of a jet aircraft engine and, more particularly, is concerned with means for providing more stable combustion in the fan stream region of the afterburner during augmentor operation in a turbofan jet engine.
2. Description of the Prior Art
In order to increase the effective thrust of the common turbojet engine, bladed fans have been added to a turbine-driven shaft thereof to effect the flow of a quantity of atmospheric air through an annular passage defined between the turbine and a radially spaced casing added thereto. The turbofan engine, as this combination has come to be known, has been found to be more efficient if the hot gas stream flow from the core engine (the basic turbojet portion of the turbofan) and the cooler air in the fan stream (the air stream forced through the annular passage by the fan) are merged together before explusion through a single discharge nozzle.
To develop still more thrust for takeoff and climb and for periods of dash of the aircraft, it is also advantageous to augment the engine thrust by burning additional fuel in an afterburner. The afterburner would be located in the turbofan engine between the turbine and the discharge nozzle at a desired location for combustion of the hot gas stream flow from the core engine and the cooler fan stream air flow from the annular passage leading from the bladed fan.
However, combustion stability of the additional fuel in the afterburner of a gas turbine engine decreases as the temperature of the inlet fan stream air to the afterburner decreases. This is a significant problem in augmented turbofan engines. To overcome this problem, large, heavy mixers are sometimes used to mix the hot gas stream flow from the core engine with the cooler fan air stream flow.
While combustion stability is improved through use of mixers of such type, other problems are created. In addition to being heavy, these mixers also produce an undesirable total pressure loss. Consequently, a need exists for improvement of the mixing of the hot core gase stream with the cooler fan air stream in a manner which does not produce undesirable side effects.